Primary clutch electronic CVT

ABSTRACT

A continuously variable transmission (CVT) is provided for use on a recreational or utility vehicle. The CVT is electronically controlled by a control unit of the vehicle. The CVT includes a primary clutch having a first sheave and a second sheave moveable relative to the first sheave. An actuator may be positioned between the primary and secondary clutches.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 61/547,485, titled “Primary Clutch Electronic CVT,”filed Oct. 14, 2011, the disclosure of which is expressly incorporatedby reference herein.

FIELD OF THE DISCLOSURE

The present disclosure relates to electronically controlledtransmissions, and more particularly to an electronically controlledcontinuously variable transmission (CVT) for recreational and utilityvehicles.

BACKGROUND AND SUMMARY

Some recreational vehicles, such as all-terrain vehicles (ATV's),utility vehicles, motorcycles, etc., include a continuously variabletransmission (CVT). In these vehicles, an actuator adjusts the positionof one of the primary and secondary clutches of the CVT. The thrustrequirement of the actuator for moving the clutch is generally dependenton the sliding friction between the movable sheave and the slidingcoupling.

Available space is often limited around the CVT for placing thecomponents of the actuator assembly. As such, actuator components havinga large package size are often difficult to place in close proximity tothe CVT. Further, the removal of some or all of the actuator componentsis often required when replacing the CVT belt.

A starting clutch is sometimes used to engage the CVT. The startingclutch is positioned at the driven or secondary clutch of the CVT toengage the secondary clutch when the CVT is in a low gear ratiocondition. Due to the low speeds and high torques of the secondaryclutch when the starting clutch engages the secondary clutch, thestarting clutch is generally large in size.

In some recreational vehicles with CVT's, such as snowmobiles, theelectrical system does not include a battery. As such, the rotationalmotion of the engine is used to generate power for the vehicle. In thesevehicles, or in vehicles that experience a sudden power loss, the clutchassembly of the CVT may require a manual reset to a home position priorto starting the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an exemplary vehicle incorporating theelectronic CVT of the present disclosure;

FIG. 2 is a perspective view of an exemplary drive system of the vehicleof FIG. 1 including a continuously variable transmission (CVT);

FIGS. 3 a and 3 b are diagrammatic views of the CVT of FIG. 2 accordingto one embodiment;

FIG. 4 is a front perspective view of an exemplary CVT of the vehicle ofFIG. 1 according to one embodiment including a housing with a cover anda mounting bracket;

FIG. 5 is a front perspective view of the CVT of FIG. 4 with the coverremoved from the mounting bracket;

FIG. 6 is a side view of a primary clutch of the CVT of FIG. 4;

FIG. 7 is a rear perspective view of the CVT of FIG. 4 illustrating anactuator assembly;

FIG. 8 is a front perspective view of the CVT of FIG. 4 illustrating amoveable sheave of the primary clutch in an open position;

FIG. 9 is a front perspective view of the CVT of FIG. 4 illustrating themoveable sheave of the primary clutch in a closed position;

FIG. 10 is an exploded front perspective view of the actuator assemblyof FIG. 7 with the mounting bracket partially cut away;

FIG. 11 is an exploded rear perspective view of the actuator assembly ofFIG. 7 with the mounting bracket partially cut away;

FIG. 12 is an exploded front perspective view of the primary clutch ofFIG. 6 and a launch clutch;

FIG. 13 is an exploded rear perspective view of the primary clutch ofFIG. 6 and the launch clutch of FIG. 12;

FIG. 14 is a cross-sectional view of the primary clutch of FIG. 6 takenalong line 14-14 of FIG. 8;

FIG. 15 is a cross-sectional view of the primary clutch of FIG. 6 takenalong line 15-15 of FIG. 9;

FIG. 16 is a perspective view of the primary clutch of FIG. 14illustrating the cross-section taken along line 14-14 of FIG. 8;

FIG. 17 is a perspective view of the primary clutch of FIG. 6 partiallycut away illustrating a sliding interface of the moveable sheave;

FIG. 18 is a partially exploded front perspective view of the primaryclutch and the launch clutch of FIG. 12;

FIG. 19 is a partially exploded rear perspective view of the primaryclutch and the launch clutch of FIG. 12;

FIG. 20 is a diagrammatic view of an exemplary electro-hydraulic circuitfor controlling the CVT of FIG. 2 according to one embodiment;

FIG. 21 is a block diagram illustrating an exemplary control strategyfor moving a clutch of the CVT of FIG. 2 to a home position;

FIG. 22 is a diagrammatic view of an exemplary control system of thevehicle of FIG. 1 without a system battery; and

FIG. 23 is a block diagram illustrating an exemplary control strategy ofthe control system of FIG. 22 for moving a clutch of the CVT of FIG. 2to a home position.

Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplification set out hereinillustrates embodiments of the invention, and such exemplifications arenot to be construed as limiting the scope of the invention in anymanner.

DETAILED DESCRIPTION OF THE DRAWINGS

The embodiments disclosed herein are not intended to be exhaustive orlimit the disclosure to the precise forms disclosed in the followingdetailed description. Rather, the embodiments are chosen and describedso that others skilled in the art may utilize their teachings.

Referring initially to FIG. 1, an exemplary vehicle 10 having anelectronically controlled CVT is illustrated. Vehicle 10 isillustratively a side-by-side ATV 10 including a front end 12, a rearend 14, and a frame or chassis 15 that is supported above the groundsurface by a pair of front tires 22 a and wheels 24 a and a pair of reartires 22 b and wheels 24 b. ATV 10 includes a pair of laterallyspaced-apart bucket seats 18 a, 18 b, although a bench style seat or anyother style of seating structure may be used. Seats 18 a, 18 b arepositioned within a cab 17 of ATV 10. A protective cage 16 extends overcab 17 to reduce the likelihood of injury to passengers of ATV 10 frompassing branches or tree limbs and to act as a support in the event of avehicle rollover. Cab 17 also includes front console 31, adjustablesteering wheel 28, and shift lever 29. Front console 31 may include atachometer, speedometer, or any other suitable instrument.

Front end 12 of ATV 10 includes a hood 32 and a front suspensionassembly 26. Front suspension assembly 26 pivotally couples front wheels24 to ATV 10. Rear end 14 of ATV 10 includes an engine cover 19 whichextends over an engine and transmission assembly (see FIG. 2). Rear end14 further includes a rear suspension assembly (not shown) pivotallycoupling rear wheels 24 to ATV 10. Other suitable vehicles may beprovided that incorporate the CVT of the present disclosure, such as asnowmobile, a straddle-seat vehicle, a utility vehicle, a motorcycle,and other recreational and non-recreational vehicles.

Referring to FIG. 2, an exemplary drive system 40 of vehicle 10 of FIG.1 is illustrated including an engine 42 and a CVT 48. CVT 48 includes aprimary or drive clutch 50 and a secondary or driven clutch 52. Anendless, variable speed belt 54 is coupled to the primary and secondaryclutches 50, 52. Engine 42 includes an engine case or housing 43 and anoutput shaft 44 configured to drive primary clutch 50 of the CVT 48.Rotation of primary clutch 50 is transferred to secondary clutch 52 viabelt 54. An output shaft 46 of secondary clutch 52 is coupled to anddrives a sub-transmission 56 which is coupled to the final drive 58 fordriving wheels 24 (see FIG. 1). In one embodiment, sub-transmission 56is geared to provide a high gear, a low gear, a reverse gear, and a parkconfiguration for vehicle 10 of FIG. 1. Fewer or additional gears may beprovided with sub-transmission 56.

An actuator assembly 80 is configured to control primary clutch 50, asdescribed herein. Actuator assembly 80 includes a motor 76 controlled bya clutch controller 36. In one embodiment, motor 76 is an electricalstepper motor, although motor 76 may alternatively be a brushed motor orother suitable electrical or hydraulic motor. In an alternativeembodiment, controller 36 and actuator assembly 80 control secondaryclutch 52 of CVT 48. Controller 36 includes a processor 38 and a memory39 accessible by processor 38 that contains software with instructionsfor controlling CVT 48. In one embodiment, controller 36 is part of anengine control unit (ECU) configured to control engine 42. In thisembodiment, a throttle operator 116 including a position sensor iscoupled to controller 36, and controller 36 electronically controls thethrottle position of engine 42 based on the detected position ofthrottle operator 116. In one embodiment, controller 36 communicateswith sensors/devices of vehicle 10 and/or other vehicle controllers viacontroller area network (CAN) communication.

In the illustrated embodiment, secondary clutch 52 is a mechanicallycontrolled clutch 52 and includes a stationary sheave and a moveablesheave (not shown). Secondary clutch 52 is configured to control thetension of belt 54 of CVT 48 as primary clutch 50 is adjusted. In oneembodiment, secondary clutch 52 includes a spring and a torque-sensinghelix (not shown). The helix applies a clamping force on belt 54proportional to the torque on secondary clutch 52. The spring applies aload proportional to the displacement of the moveable sheave. In oneembodiment, secondary clutch 52 provides mechanical load feedback forCVT 48.

As illustrated in FIGS. 3A and 3B, primary clutch 50 is coupled to androtates with a shaft 70, and secondary clutch 52 is coupled to androtates with a shaft 72. Shaft 70 is driven by the output shaft 44 ofengine 42 (see FIG. 2). Shaft 72 of secondary clutch 52 drivessub-transmission 56 (see FIG. 2). Belt 54 wraps around the primary andsecondary clutches 50, 52 and transfers rotational motion of primaryclutch 50 to secondary clutch 52.

Referring to FIG. 4, a housing 60 for CVT 48 is illustrated with a cover61 coupled to a back plate or mounting bracket 62. Flanged portions 64a, 64 b of mounting bracket 62 and cover 61, respectively, areillustratively configured to receive fasteners 74 (see FIG. 7) to couplecover 61 to mounting bracket 62. Fasteners 74 are illustratively boltsor screws, although other suitable fasteners 74 may be used. Cover 61includes a pipe portion 68 forming an opening 69 to provide access tobelt 54 of CVT 48. For example, opening 69 may be used to visuallyinspect belt 54 and/or secondary clutch 52 (see FIG. 2) or to check thetension of belt 54. Mounting bracket 62 includes a vent structure 66including a pair of vents 67 a, 67 b extending into the interior ofhousing 60 (see FIG. 5). Vents 67 a, 67 b and opening 69 cooperate toprovide airflow to CVT 48 to reduce the likelihood of the components ofCVT 48 overheating. Vent structure 66 is illustratively coupled tomounting bracket 62 via fasteners 75 (see FIG. 7), although ventstructure 66 may alternatively be integrally formed with mountingbracket 62 or cover 61. Cover 61 is removable from mounting bracket 62upon removing fasteners 74 from flanged portions 64 a, 64 b. Asillustrated in FIG. 5, cover 61 is adapted to be pulled away frommounting bracket 62 in a direction substantially perpendicular to thesurface of mounting bracket 62.

Referring to FIG. 5, primary clutch 50 of CVT 48 is secured to mountingbracket 62 via a bracket 90. Bracket 90 includes flanged portions 94each adapted to receive a fastener (not shown) to couple bracket 90 tomounting bracket 62. Bracket 90 illustratively includes an end wall 96and a curved wall 98 (see FIG. 10) that extends perpendicularly betweenend wall 96 and mounting bracket 62. In the illustrated embodiment,curved wall 98 extends partially around the outer circumference ofprimary clutch 50. A pair of posts 92 further support bracket 90 betweenend wall 96 and mounting bracket 62. Posts 92 are illustratively pressfit between flanged portions 99 of end wall 96 and mounting bracket 62,although posts 92 may alternatively be coupled to end wall 96 and/ormounting bracket 62 with fasteners. A position sensor 114 is coupled toa flange 115 (see FIG. 11) of bracket 90 for detecting the axiallocation of a moveable sheave 102 of primary clutch 50. In oneembodiment, position sensor 114 is a rotary sensor with a bell crank,although a linear sensor or other suitable sensor may be provided.Sensor 114 provides position feedback to controller 36 (FIG. 2).

As illustrated in FIG. 5, primary clutch 50 includes a pair of sheaves100, 102 that are supported by and rotate with shaft 70. Sheaves 100,102 cooperate to define a pulley or slot 104 within which belt 54 (seeFIG. 2) rides. As illustrated in FIG. 6, slot 104 is substantiallyV-shaped due to slanted inner surfaces 110, 112 of respective sheaves100, 102. Accordingly, belt 54 has a substantially V-shapedcross-section to cooperate with inner surfaces 110, 112 of the sheaves100, 102. Primary clutch 50 further includes a screw assembly includingan outer screw assembly 120 and an inner screw assembly 122 positionedbetween outer screw assembly 120 and moveable sheave 102.

In the illustrated embodiment, sheave 100 is stationary axially in adirection parallel to the axis of shaft 70, and sheave 102 is movableaxially in a direction parallel to the axis of shaft 70. In particular,sheave 102 is configured to slide along shaft 70 to a plurality ofpositions between a fully extended or open position (see FIGS. 8 and 14)and a fully closed or retracted position (see FIGS. 9 and 15). Withmoveable sheave 102 in a fully extended or open position, slot 104 is ata maximum axial width, and belt 54 rides near the radial center ofprimary clutch 50, as illustrated in FIG. 14. In the illustratedembodiment, belt 54 does not contact a tube portion 216 of a slidingsupport 200 of primary clutch 50 when moveable sheave 102 is at thefully open position of FIG. 14. With moveable sheave 102 in a fullyretracted or closed position, slot 104 is at a minimum axial width, andbelt 54 rides near the outer periphery of primary clutch 50, asillustrated in FIG. 15. Secondary clutch 52 (see FIG. 2) is similarlyconfigured with a pair of sheaves (not shown) supported by and rotatablewith shaft 72. One sheave of secondary clutch 52 is axially movable, andthe other sheave is axially stationary. In one embodiment, secondaryclutch 52 is configured to control the tension of belt 54. For purposesof illustrating primary clutch 50, secondary clutch 52 and belt 54 arenot shown in FIGS. 5, 8, and 9.

Movement of sheave 102 of primary clutch 50 and movement of the moveablesheave of secondary clutch 52 provides variable effective gear ratios ofCVT 48. In one embodiment, CVT 48 is configured to provide an infinitenumber of effective gear ratios between minimum and maximum gear ratiosbased on the positions of the moveable sheaves of the clutches 50, 52.In the configuration illustrated in FIG. 3A, the moveable sheave 102(see FIG. 6) of primary clutch 50 is substantially opened, and themoveable sheave (not shown) of secondary clutch 52 is substantiallyretracted. Accordingly, a low gear ratio is provided by CVT 48 in theconfiguration of FIG. 3A such that shaft 72 of secondary clutch 52rotates slower than shaft 70 of primary clutch 50. Similarly, in theconfiguration illustrated in FIG. 3B, the moveable sheave 102 (see FIG.6) of primary clutch 50 is substantially retracted, and the moveablesheave (not shown) of secondary clutch 52 is substantially opened.Accordingly, a high gear ratio is provided by CVT 48 in theconfiguration of FIG. 3B such that shaft 72 of secondary clutch 52rotates faster than shaft 70 of primary clutch 50.

As illustrated in FIG. 7, actuator assembly 80 is coupled to the back ofmounting bracket 62. Actuator assembly 80 is configured to move themoveable sheave 102 (see FIG. 5) of primary clutch 50, as describedherein. In the illustrative embodiment, engine 42 and sub-transmission56 (see FIG. 2) are configured to be positioned adjacent the back ofmounting bracket 62 on either side of actuator assembly 80. Inparticular, engine 42 is positioned to the right of actuator assembly 80(as viewed from FIG. 7), and the output of engine 42 couples to shaft 70of primary clutch 50 through an opening 82 of mounting bracket 62.Similarly, sub-transmission 56 is positioned to the left of actuatorassembly 80 (as viewed from FIG. 7), and shaft 72 of secondary clutch 52(see FIG. 3A) extends through an opening 84 of mounting bracket 62 todrive sub-transmission 56.

As illustrated in FIGS. 10 and 11, actuator assembly 80 includes motor76 with a geared output shaft 132, a reduction gear 130 housed within agear housing 78, and a main gear drive 86 extending outwardly from thefront of mounting bracket 62. Reduction gear 130 includes first andsecond gears 134, 136 coupled to a shaft 135. First gear 134 engagesgeared output shaft 132 of motor 76, and second gear 136 engages a firstgear 106 coupled to an end of a shaft 109 of main gear drive 86. Maingear drive 86 further includes a second gear 108 coupled to an end ofshaft 109 opposite first gear 106. Second gear 108 engages an outer gear126 of screw assembly 120 (see FIG. 6) of primary clutch 50.

Gear housing 78 includes flange portions 156 each configured to receivea fastener 158 (see FIG. 7) for coupling gear housing 78 to the back ofmounting bracket 62. Gear housing 78 includes a first portion 150, asecond or intermediate portion 152, and a third portion 154. Firstportion 150 includes an opening 151 (see FIG. 11) that receives outputshaft 132 of motor 76. Second portion 152 includes an opening 153 (seeFIG. 10) that receives reduction gear 130. Reduction gear 130 issupported at one end by second portion 152 and at the other end by asupport member 140 mounted on the front face of mounting bracket 62.Bearings 142, 146 are positioned at opposite ends of shaft 135 tofacilitate rotation of reduction gear 130 within second portion 152 andsupport member 140, respectively. Third portion 154 of housing 78 housesa portion of first gear 106 and supports the end of shaft 109 adjacentfirst gear 106. Similarly, end wall 96 of bracket 90 supports the otherend of shaft 109 adjacent second gear 108. As illustrated in FIG. 11,bearings 144, 148 are coupled at opposite ends of shaft 109 tofacilitate rotation of main gear drive 86 relative to gear housing 78and bracket 90. In particular, bearing 148 is received within thirdportion 154 of gear housing 78, and bearing 144 is received within anopening 95 formed in end wall 96 of bracket 90.

Referring to FIGS. 12-16, outer screw assembly 120 of primary clutch 50includes a neck portion 128 and a threaded screw portion 127. Neckportion 128 extends through an opening 97 formed in end wall 96 ofbracket 90 (see FIG. 10). An outer bearing support 184 is rotatablycoupled to neck portion 128 via bearing assembly 183 and is fixedlycoupled to an end 71 of shaft 70. As such, shaft 70 and outer bearingsupport 184 rotate together independently from outer screw assembly 120.In the illustrated embodiment, end 71 of shaft 70 is press fit intoouter bearing support 184. End 71 further includes a circumferentialchannel 73 that engages an inner ridge 189 of outer bearing support 184(see FIG. 14). End 71 of shaft 70 may also be fastened to outer bearingsupport 184 with an adhesive or other suitable fastener.

Inner screw assembly 122 includes a plate portion 186 and a threadedscrew portion 188 positioned radially inwardly from plate portion 186.An L-shaped wall 185 is illustratively coupled between plate portion 186and screw portion 188 forming a radial gap 187 between screw portion 188and wall 185. Screw portion 188 includes outer threads 196 that matewith inner threads 129 of screw portion 127 of outer screw assembly 120.Screw portion 127 of outer screw assembly 120 is received within gap 187formed in inner screw assembly 122 (see FIGS. 14-16). An o-ring seal 192positioned radially inside of wall 185 is configured to abut screwportion 127 of outer screw assembly 120. Plate portion 186 of innerscrew assembly 122 includes flanges 124 having apertures 125 (see FIGS.12 and 13) that slidably receive posts 92 of bracket 90 (see FIGS. 8 and9). Plate portion 186 further includes slots 194 circumferentiallyspaced near the outer perimeter of plate portion 186.

Still referring to FIGS. 12-16, a sliding assembly of primary clutch 50includes a bushing assembly 172, a sliding support 200, and a bearingassembly 190 positioned between bushing assembly 172 and inner screwassembly 122. Bushing assembly 172 of primary clutch 50 includes a neckportion 176 that receives shaft 70 therethrough and a plurality offlanges 174 that couple to circumferentially spaced seats 202 ofmoveable sheave 102. A plurality of fasteners 173, illustratively screws173, are received by corresponding apertures of flanges 174 and seats202 to couple bushing assembly 172 to sheave 102. A bushing 178positioned within neck portion 176 engages shaft 70 and supports theoutboard end of moveable sheave 102. Shaft 70 is configured to rotateinside of bushing 178 at engine idle (when primary clutch 50 isdisengaged) and to rotate with bushing 178 when primary clutch 50 isengaged. Bushing 178 is configured to provide a low-friction surfacethat slides along shaft 70 during movement of sheave 102. Bushing 178may alternatively be a needle bearing.

Neck portion 176 of bushing assembly 172 is rotatably coupled to screwportion 188 of inner screw assembly 122 via bearing assembly 190positioned within screw portion 188. A collar 182 and a toothed lockwasher 180 are coupled to neck portion 176 extending through screwportion 188 (see FIGS. 14-16). Lock washer 180 illustratively includesan inner tab 181 (see FIG. 12) that engages a corresponding slot 177(see FIG. 12) in the outer surface of neck portion 176 such that lockwasher 180 rotates with bushing assembly 172. Collar 182 is threadedonto neck portion 176 and is rotatably fixed in place on neck portion176 with tabbed lock washer 180. Accordingly, bushing assembly 172,sheaves 100, 102, collar 182, washer 180, and outer bearing support 184are configured to rotate with shaft 70, while outer screw assembly 120and inner screw assembly 122 do not rotate with shaft 70. Bushingassembly 172 is configured to slide axially along shaft 70 via bearing178.

Sliding support 200 is coupled to sheaves 100, 102 to provide a slidinginterface for moveable sheave 102 relative to stationary sheave 100. Asillustrated in FIGS. 14-16, sliding support 200 includes a tube portion216 and a plate portion 214 coupled to and substantially perpendicularto tube portion 216. In one embodiment, plate portion 214 and tubeportion 216 are molded together, although plate and tube portions 214,216 may be coupled together with a fastener or by other suitablecoupling means. Plate and tube portions 214, 216 each rotate withsheaves 100, 102 and shaft 70. A pair of seals 220 a, 220 b and a clutch218 positioned between seals 220 a, 220 b are coupled between tubeportion 216 and shaft 70. Clutch 218 is illustratively a one-way clutch218 that free-wheels during vehicle idle and that locks tube portion 216to shaft 70 during engine braking. As such, one-way clutch 218 acts as abearing between tube portion 216 and shaft 70 during idling conditionsand locks tube portion 216 to shaft 70 when CVT 48 is being drivenfaster than engine 42 (i.e., when belt 54 and clutch 50 work tooverdrive engine 42 of FIG. 2).

As illustrated in FIG. 12, plate portion 214 includes a plurality ofsliding couplers 206 that are circumferentially spaced around the outerdiameter of plate portion 214. In the illustrated embodiment, the outerdiameter of plate portion 214 is nearly the same as the outer diameterof moveable sheave 102 such that couplers 206 of plate portion 214 areimmediately adjacent an inner cylindrical wall 203 of sheave 102.Couplers 206 are illustratively clips 206 that are configured toslidingly receive corresponding sliding members or ridges 204 that arecircumferentially spaced around inner wall 203 of moveable sheave 102.Ridges 204 extend radially inward from and substantially perpendicularto cylindrical inner wall 203. Ridges 204 illustratively include aradial width and a radial height that is substantially greater than theradial width. As illustrated in FIG. 17, a low-friction liner 208 ispositioned in each clip 206 to engage the sliding surface of ridges 204.In one embodiment, liner 208 is a low-friction composite or plasticmaterial, such as polyether ether ketone (PEEK), polyimide-based plastic(e.g. Vespel), or nylon, for example, with additives to reduce friction.As illustrated in FIGS. 14-16, a cylindrical bearing or bushing 222 andan o-ring seal 224 are positioned between moveable sheave 102 and tubeportion 216 to locate sheave 102 radially onto tube portion 216. Bushing222 provides a low friction sliding surface for sheave 102 relative totube portion 216. In one embodiment, grease is provided in theinterfaces between ridges 204 and clips 206 and between bushing 222 andtube portion 216 to reduce sliding friction.

Moveable sheave 102 is configured to slide relative to sliding support200 along ridges 204 of FIG. 12. In one embodiment, the sliding frictionbetween sheave 102 and sliding support 200 is minimized with the slidinginterface between couplers 206 and ridges 204 being near the outerdiameter of moveable sheave 102. In the illustrated embodiment, theouter diameter of moveable sheave 102 is large relative to the outerdiameters of shaft 70 and tube portion 216. In one embodiment, the outerdiameter of moveable sheave 102 is at least three times greater than theouter diameters of shaft 70 and tube portion 216.

As illustrated in FIGS. 14-16, bearing assemblies 183 and 190 are eachpositioned outside of the outer profile of moveable sheave 102. Inparticular, referring to FIG. 14, bearing assemblies 183, 190 arepositioned axially outside of the end of sheave 102 lying in plane 198.As such, bearing assemblies 183, 190 are axially spaced apart from thesliding interfaces formed with couplers 206 and ridges 204 and withbushing 222 and tube portion 216. In one embodiment, bearing assemblies183, 190 include angular contact bearings, although other suitablebearings may be used. Neck portion 176 of bushing assembly 172 is alsoillustratively positioned outside of the outer profile of moveablesheave 102, as illustrated in FIG. 14.

In operation, the actuation of gear drive 86 by motor 76 (see FIG. 10)is configured to modulate the gear ratio provided by primary clutch 50.Referring to FIG. 10, the output of motor 76 is transferred throughreduction gear 130 to main gear drive 86 to thereby rotate outer screwassembly 120 (see FIG. 8) of primary clutch 50. Outer screw assembly 120is stationary axially and rotates due to the rotation of main gear drive86 independent of a rotation of shaft 70. Referring to FIGS. 8 and 14,rotation of outer screw assembly 120 in a first direction unscrewsthreaded screw portion 188 of inner screw assembly 122 from threadedscrew portion 127 of outer screw assembly 120, thereby causing innerscrew assembly 122 to slide axially along posts 92 towards stationarysheave 100 while remaining rotationally stationary.

Referring to FIG. 14, the axial movement of inner screw assembly 122provides a thrust force against moveable sheave 102 via bushing assembly172 to move sheave 102 towards stationary sheave 100. As describedherein, bushing assembly 172 rotates within the rotationally stationaryinner screw assembly 122 via bearing assembly 190. As such, the thrustforce provided by inner screw assembly 122 is applied to bushingassembly 172 through bearing assembly 190. Similarly, rotation of outerscrew assembly 120 in a second, opposite direction causes inner screwassembly 122 to move axially away from stationary sheave 100 along posts92 (see FIG. 8) and to apply a pulling force on bushing assembly 172 andmoveable sheave 102 through bearing assembly 190. Bearing assemblies183, 190 provide axial movement of inner screw assembly 122, bushingassembly 172, and sheave 102 relative to shaft 70 that is independentfrom the rotational movement of shaft 70, sheaves 100, 102, slidingsupport 200, and bushing assembly 172. In the illustrated embodiment,the range of axial motion of inner screw assembly 122 relative to outerscrew assembly 120 defines the maximum and minimum gear ratios providedwith primary clutch 50, although other limit stops may be provided.

As illustrated in FIGS. 18 and 19, a clutch assembly 170 is coupled toshaft 70 to serve as a starting or launch clutch for primary clutch 50.Clutch assembly 170 is illustratively a dry centrifugal clutch 170integrated into primary clutch 50. Clutch assembly 170 is configured tobe positioned external to the engine case 43 (see FIG. 2) of engine 42.As such, clutch assembly 170 is not integrated with the engine case 43of engine 42 and is therefore not positioned in the engine oil. Rather,clutch assembly 170 is positioned outside of the engine case 43 and iscoupled to the output shaft 44 of engine 42 to operate as a dry startingclutch for primary clutch 50. As such, clutch assembly 170 is removablefrom engine 42 by pulling the clutch assembly 170 from shaft 44.

In assembly, clutch assembly 170 is positioned in an interior 209 ofprimary clutch 50 (see FIG. 19). Clutch assembly 170 includes an endplate 232 coupled to shaft 70 and having a plurality of posts 234. Inthe illustrated embodiment, shaft 70 and end plate 232 are integrallyformed, although shaft 70 may be coupled to end plate 232 using afastener or press-fit configuration. As illustrated in FIG. 14, shaft 70includes substantially cylindrical outer and inner surfaces 226, 228,respectively. Inner surface 228 forms a hollow interior region 229 ofshaft 70. Outer and inner surfaces 226, 228 illustratively taper fromend plate 232 towards end 71. The outer surface of shaft 70 furtherincludes a step 88 such that the diameter of the portion of shaft 70received by bushing assembly 172 and outer bearing support 184 issmaller than the diameter of the portion of shaft 70 positioned in tubeportion 216 of sliding support 200. In the illustrated embodiment, theoutput shaft 44 of engine 42 (see FIG. 2) is received by interior region229 of shaft 70 to drive rotation of clutch assembly 170. As such,clutch assembly 170 and shaft 70 rotate with engine 42.

Referring to FIGS. 18 and 19, clutch assembly 170 further includes shoesor arms 238 pivotally mounted to posts 234 via fasteners 240. Arms 238each include an aperture 236 that receives a corresponding post 234 ofend plate 232. Fasteners 240 illustratively include bolts and washers.Each arm 238 includes a friction pad 230 coupled to the outercircumferential surface of each arm 238. A spring 242 is coupled betweenadjacent arms 238 at seats 244 to bias arms 238 into spaced relationwith each other.

In the illustrated embodiment, clutch assembly 170 is disengaged fromprimary clutch 50 when engine 42 (see FIG. 2) is at or below engine idlespeed. As the engine speed and the corresponding rotational speed ofclutch assembly 170 increases, the centrifugal force acting on arms 238overcomes the biasing force of springs 242 and causes ends 246 of arms238 to swing radially outward, thereby forcing friction pads 230 intoengagement with an inner friction surface 210 (see FIG. 13) ofstationary sheave 100. The engagement of clutch assembly 170 withstationary sheave 100 transfers torque to sliding support 200 andmoveable sheave 102. As such, sheaves 100, 102, sliding support 200, andbushing assembly 172 all rotate with shaft 70. When the rotational speedof shaft 70 decreases to a threshold speed, the reduced centrifugalforce causes arms 238 to move radially inward away from surface 210 ofsheave 100. As such, clutch assembly 170 disengages primary clutch 50.Stationary sheave 100 illustratively includes a plurality ofcircumferentially spaced cooling fins 212 configured to reduce the heatgenerated by the engagement of clutch assembly 170.

In the illustrated embodiment, upon removing cover 61 and bracket 90from mounting bracket 62 (see FIG. 5), a disengaged centrifugal startingclutch 170 allows primary clutch 50 to be pulled off shaft 70 as oneassembled unit. Belt 54 (see FIG. 2) may be removed and/or replaced uponremoving primary clutch 50 from shaft 70. Further, actuator assembly 80(see FIGS. 9 and 10) remains coupled to mounting bracket 62 when primaryclutch 50 is removed from shaft 70 such that the gears of actuatorassembly 80 (e.g. reduction gear 130) are not required to be removed andreset or recalibrated. In one embodiment, primary clutch 50 and belt 54are removable from shaft 70 without removing main gear drive 86 (seeFIG. 5).

Centrifugal starting clutch 170 serves to separate the shifting functionof primary clutch 50 from the engagement function of the primary clutch50. In particular, the shifting function is performed by the primaryclutch 50 via controller 36 (see FIG. 6), while the engagement ofprimary clutch 50 is controlled by starting clutch 170. As such,controller 36 is not required to control the engagement of primaryclutch 50 because starting clutch 170 automatically engages primaryclutch 50 upon reaching a predetermined rotational speed.

In an alternative embodiment, primary clutch 50 may be configured tooperate without a starting clutch 170. For example, in this embodiment,primary clutch 50 of CVT 48 is directly coupled to the output of engine42. When vehicle 10 is at idle or not running, controller 36 positionsmoveable sheave 102 away from stationary sheave 100 such that belt 54 ispositioned radially inward towards shaft 70, as illustrated in FIG. 6.In one embodiment, controller 36 positions sheave 102 at a maximum openposition when engine 42 is idling or not running such that moveablesheave 102 does not contact belt 54. In one embodiment, sheave 102 isdisengaged from belt 54 during shifting of sub-transmission 56 (see FIG.2). As such, secondary clutch 52 is rotating at a zero or minimal speedupon shifting sub-transmission 56. Engagement of sheave 102 and belt 54is initiated upon engine driving torque being requested, e.g. uponthrottle request by an operator. In another embodiment, sheave 102 ismoved into engagement with belt 54 after sub-transmission 56 is shiftedout of neutral and into gear. In another embodiment, moveable sheave 102is spring-loaded away from belt 54 during engine idle, and the shiftingof sub-transmission 56 into gear mechanically causes sheave 102 to moveback into engagement with belt 54.

In one embodiment, controller 36 of FIG. 2 provides a spike loadreduction feature configured to automatically shift CVT 48 upondetection of vehicle 10 being airborne. For example, when vehicle 10 ofFIG. 1 is airborne, wheels 24 may accelerate rapidly due to the wheels24 losing contact with the ground while the throttle operator 116 (seeFIG. 2) is still engaged by the operator. When the wheels 24 again makecontact with the ground upon vehicle 10 landing, the wheel speeddecelerates abruptly, possibly leading to damaged or stressed componentsof the CVT 48 and other drive train components. Controller 36 initiatesspike load control upon detection of vehicle 10 being airborne to slowdrive train acceleration of the airborne vehicle 10. In one embodiment,controller 36 slows the rate at which CVT 48 upshifts during spike loadcontrol. In one embodiment, controller 36 stops upshifting of CVT 48 atleast momentarily during spike load control or downshifts CVT 48 to alower gear ratio. As such, the drive train acceleration of vehicle 10 isslowed before vehicle 10 returns to the ground, and the inertial loadingon CVT 48 and other drive train components (e.g. sub-transmission 56,final drive 58, etc.) upon vehicle 10 landing is reduced or minimized.In one embodiment, controller 36 automatically adjusts the gear ratio ofCVT 48 of the airborne vehicle 10 such that the wheel speed upon vehicle10 returning to the ground is substantially the same as the detectedwheel speed immediately prior to vehicle 10 becoming airborne.

In one embodiment, controller 36 determines that vehicle 10 is airborneupon detection of a sudden acceleration in drive train components. Forexample, controller 36 may detect the sudden acceleration based onfeedback from a wheel speed sensor, engine speed sensor, transmissionspeed sensor, or other suitable speed sensor on the drive train ofvehicle 10. In the illustrated embodiment, controller 36 continuouslymonitors the angular acceleration of the drive train by measuring thespeed of one of the shafts of CVT 48 or sub-transmission 56 with a speedsensor 59. Vehicle 10 is determined to be airborne when the accelerationin wheel speed or drive train speed exceeds the design specifications ofvehicle 10. For example, vehicle 10 has a maximum wheel accelerationbased on available torque from engine 42, the frictional force from theground, the weight of vehicle 10, and other design limits. When themonitored drive train components accelerate at a faster rate thanvehicle 10 is capable under normal operating conditions (i.e., whenwheels 24 are in contact with the ground), controller 36 determines thatwheels 24 have lost contact with the ground. One or more predeterminedacceleration limits are stored at controller 36 that correspond to thedesign limits of vehicle 10 to trigger the spike load control.

In one embodiment, the spike load reduction feature of controller 36works in conjunction with a drive train protection feature that uses anelectronic throttle control system to reduce drive train acceleration(i.e., by reducing the throttle opening, etc.) upon detection of anairborne condition, as described in U.S. patent application Ser. No.13/153,037, filed on Jun. 3, 2011 and entitled “Electronic ThrottleControl,” the disclosure of which is incorporated herein by reference.In some operating conditions, a high or increasing throttle demand isprovided with throttle operator 116 while vehicle 10 is airborne. In oneembodiment, the engine 42 continues to rev due to the high throttledemand until a rev limit of the engine 42 is reached. In a vehicle 10having electronic throttle control, airflow to the engine 42 isautomatically restricted upon detection of the airborne condition toreduce engine power and to reduce the likelihood of reaching the revlimit.

Controller 36 may detect an airborne condition of vehicle 10 using othermethods, such as by detecting the compression distance or height of asuspension system (e.g. front suspension assembly 26 of FIG. 1) ofvehicle 10 with a suspension height sensor and/or by monitoring enginetorque and power, as described in the referenced U.S. patent applicationSer. No. 13/153,027.

In one embodiment, controller 36 provides a plurality of operating modesfor CVT 48. Exemplary operating modes, illustratively selectable by anoperator with operating mode selector 113, include performance, economy,manual mimic, cruise control, and hydrostatic modes. In one embodiment,the performance and economy modes are selectable for each of the manualmimic, cruise control, and hydrostatic modes. In one embodiment, theoperating modes are only selectable when vehicle 10 is moving below apredetermined vehicle speed, such as below 10 mph, for example, althoughother suitable threshold speeds may be provided. In one embodiment, oneor more of the operating modes are selectable only when vehicle 10 issubstantially stopped.

The performance and economy modes are illustratively automatic modeswherein controller 36 actively controls CVT 48 based on engine speed,the position of throttle operator 116 and/or the throttle valve, andvehicle speed. In the economy mode, primary clutch 50 is adjusted basedon engine speed according to a brake specific fuel consumption mapstored at memory 39 of controller 36. In particular, CVT 48 and engine42 cooperate to provide an improved fuel economy as compared with theperformance mode. In a performance mode, primary clutch 50 is adjustedbased on engine speed such that peak power is output for a given enginespeed and/or other operating condition. As such, the performance modeprovides improved vehicle performance as compared with the economy mode.

In the cruise control mode, at least one of the engine throttle positionand the gear ratio of CVT 48 is held constant to hold the vehicle speedat a predetermined vehicle speed. In one embodiment, the throttleposition of engine 42 is locked or held constant to hold the enginetorque substantially constant, and the gear ratio of CVT 48 is variedbased on vehicle speed feedback to maintain the target vehicle speed. Inanother embodiment, the gear ratio of CVT 48 is held constant duringcruise control while the throttle position of engine 42 is varied tomaintain the target vehicle speed. Alternatively, both the throttleposition and the gear ratio of CVT 48 may be held substantially constantor may be simultaneously adjusted to control vehicle speed.

In the hydrostatic mode, the engine speed and the gear ratio of CVT 48are controlled independently by an operator. For example, the enginespeed is selected (e.g. with throttle operator 116 or another suitableinput device) based on a particular use or application, i.e., forpowering vehicle implements, for charging system capacity, etc. The gearratio of CVT 48 is selected by a separate input device, such as a pedallever, or joystick. In one embodiment, the hydrostatic mode is providedin a controller 36 that also includes electronic throttle controlfunctionality, as described herein, or in a vehicle 10 that includes anengine speed governor.

In a manual mimic mode, controller 36 shifts CVT 48 between a pluralityof discrete gear ratios to simulate a traditional manual or automatictransmission. In particular, primary clutch 50 is moved to a pluralityof predetermined positions during operation that each correspond to adifferent gear ratio. For example, in a first gear, primary clutch 50 ismoved to a first predetermined position providing a first gear ratio.When CVT 48 is shifted to a second gear, primary clutch 50 is moved to asecond predetermined position providing a second gear ratio higher thanthe first gear ratio. Each predetermined position of primary clutch 50corresponds to a different gear ratio.

In one embodiment, an operator inputs a shift command to controller 36to initiate a gear shift in the manual mimic mode, further simulatingoperation of a traditional manual or semi-automatic transmission. Forexample, shift lever 29 (see FIG. 1) of vehicle 10 may be used for theselection of each discrete gear ratio by the operator. Other exemplaryshifters include a switch, paddle, or knob. Alternatively, controller 36shifts CVT 48 automatically between each predefined discrete gear ratio.In one embodiment, primary clutch 50 is moved to five or sixpredetermined positions across the displacement range of primary clutch50 to provide five or six discrete gear ratios of CVT 48, although feweror additional gear ratios may be provided. In one embodiment, ignitionto engine 42 (FIG. 2) is momentarily cut as primary clutch 50 movesbetween each predetermined position. In particular, one or more sparkplugs of engine 42 are cut during the transition between discrete gearratios to simulate the inertia shift experienced in a vehicle 10 havinga traditional manual or automatic transmission. Other torqueinterruption of engine 42 may be used to simulate traditionaltransmission shifting.

In one embodiment, CVT 48 further includes a planetary gear assembly toprovide an infinitely variable transmission system. In one embodiment,the planetary gear assembly consists of a ring gear, several planetarygears coupled to a carrier, and a sun gear. The ring gear is drivendirectly off the output of engine 42 via a gear or chain. The planetarygears and the carrier are connected to and driven by the secondaryclutch 52. The sun gear serves as the output of CVT 48 connected to thesub-transmission 56. Based on the gear ratios of the planetary gearassembly, the combined CVT 48 and planetary gear assembly are configuredto provide both positive and negative speeds (forward and reverse) byvarying the gear ratio of the CVT 48. In one embodiment, the hydrostaticmode provided with controller 36 and described herein is implemented ina CVT 48 having a planetary gear assembly.

In one embodiment, CVT 48 is electro-hydraulically actuated, asillustrated with the exemplary electro-hydraulic circuit 278 of FIG. 20.In the illustrated embodiment of FIG. 20, primary clutch 50 of CVT 48 isactuated by electro-hydraulic circuit 278 rather than by actuatorassembly 80 of FIGS. 10 and 11. Circuit 278 may also be configured tocontrol secondary clutch 52. Electro-hydraulic circuit 278illustratively includes a hydraulic circuit 282 and an electric circuit284. Controller 36 illustratively receives analog inputs 250, digitalinputs 252, and CAN inputs 254. Exemplary analog and digital inputs 250,252 include hydraulic system pressure sensors, a clutch position sensor(e.g. sensor 290 of FIG. 20), a servo valve position sensor, and othersensors detecting various parameters of vehicle 10. Exemplary CAN inputs254 include an engine speed sensor, throttle position sensor, vehiclespeed sensor, vehicle operating mode sensor, and other CAN based sensorsthat detect various parameters of vehicle 10. Controller 36 isconfigured to control an electric motor 262 of electric circuit 284 anda pump 264 and a servo valve 272 of hydraulic circuit 282 based oninputs 250, 252, 254.

A motor driver 256 is configured to control the power provided to motor262 based on control signals from controller 36. Alternatively, a relaymay be provided in place of motor driver 256 that is selectivelyactuated by controller 36 to provide fixed power to motor 262. Motor 262may be any motor type suitable for driving pump 264. In the illustratedembodiment, motor 262 is a DC electric motor. A voltage supply 261,illustratively 12 VDC, is provided to motor 262, and the speed of motor262 is controlled by controller 36 via motor driver 256. An output 263of motor 262 drives pump 264. In the illustrated embodiment, pump 264 isa variable displacement pump 264. A pump control unit 258 of controller36 modulates the displacement of pump 264 to control hydraulic pressureof hydraulic circuit 282 based on inputs 250, 252, 254. Pump 264 mayalternatively be a fixed displacement pump.

A hydraulic accumulator 268 stores pressurized hydraulic fluid to assistpump 264 and motor 262 with meeting the pressure demands of hydrauliccircuit 282. For example, accumulator 268 is configured to achieverequired pressure demands of hydraulic circuit 282 during peak shiftrates of CVT 48. As such, the likelihood of spike loads being induced onthe electric circuit 284 during peak shift rates of CVT 48 is reduced. Apressure relief valve 270 is provided to maintain the pressure onhydraulic line 288 below a predetermined maximum threshold pressure.Pressure relief valve 270, pump 264, and servo valve 272 are coupled toa hydraulic return reservoir 280.

Servo valve 272 regulates the flow of hydraulic fluid from line 288 toactuator 274 to adjust the position of moveable sheave 102. Servo valve272 is illustratively a three-way electro-hydraulic servo valve 272controlled by a servo valve driver 260 of controller 36. Servo valvedriver 260 of controller 36 controls servo valve 272 based on inputs250, 252, 254. Actuator 274, illustratively a linear hydraulic actuator,includes a piston 275 coupled to moveable sheave 102 via a rotarybearing 276. In one embodiment, rotary bearing 276 is a flanged bearingor a face bearing, although another suitable bearing 276 may beprovided. In one embodiment, actuator 274 is coupled to chassis 15 ofvehicle 10 (see FIG. 1), and moveable sheave 102 rotates about piston275 of actuator 274 and moves axially relative to actuator 274 viabearing 276. Servo valve 272 is coupled to actuator 274 via hydrauliclines 286. In one embodiment, lines 286 are small diameter, highpressure hydraulic lines 286. By regulating the fluid flow to actuator274 with servo valve 272, linear displacement of actuator 274 isadjusted to cause corresponding axial adjustment of moveable sheave 102.

In one embodiment, electric circuit 284 and hydraulic circuit 282 arepositioned on vehicle 10 (see FIG. 1) away from CVT 48, and actuator 274is positioned immediately adjacent or within housing 60 (see FIG. 4) ofCVT 48. As such, hydraulic lines 286 are routed from servo valve 272 tothe actuator 274 positioned near CVT 48. For example, electric circuit284 and hydraulic circuit 282 may be placed beneath hood 32 and/or seats18 a, 18 b (see FIG. 1), and CVT 48 and actuator 274 may be positionedtowards the rear end 14 of vehicle 10 beneath engine cover 19 (see FIG.1). As such, the actuation components (i.e. actuator 274) of themoveable sheave(s) 102 of CVT 48 occupy a small space at the location ofCVT 48 while some or all of the remaining components ofelectro-hydraulic circuit 278 are positioned elsewhere on vehicle 10.

In one embodiment, the pressure applied to moveable sheave 102 viaactuator 274 is modulated to achieve a desired gear ratio of CVT 48and/or a desired pinch force on belt 54. As illustrated in FIG. 20, aposition sensor 290 is configured to detect the linear position ofmoveable sheave 102 and provide a corresponding signal to controller 36with the detected position data. As such, the position of sheave 102 maybe monitored during operation.

In one embodiment, controller 36 implements a fail-safe mode in thecontrol of moveable sheave 102. In particular, when a system failure orsignal loss is detected by controller 36, moveable sheave 102 ispositioned to a maximum low ratio or open position such that the pinchforce on belt 54 is minimized or removed. An exemplary system failure iswhen no or inadequate hydraulic pressure in hydraulic circuit 282 isdetected with inputs 250, 252.

The electronically controlled clutch 50, 52 of CVT 48 is configured tomove to a home position prior to or upon shutting down vehicle 10. Forexample, the controlled clutch 50, 52 moves to its fully open position(see FIG. 8, for example) or to its fully closed position (see FIG. 9,for example). In the illustrated embodiment, upon vehicle shutdown,moveable sheave 102 of primary clutch 50 moves to its furthest openposition, as illustrated in FIG. 8. As such, moveable sheave 102 ispositioned away from belt 54 prior to vehicle 10 being started, therebyreducing the likelihood of vehicle 10 taking off upon starting engine42. In one embodiment, for an electronically controlled secondary clutch52, the moveable sheave (not shown) of secondary clutch 52 moves to itsfurthest closed position.

Referring to FIG. 2, vehicle 10 includes a system battery 118 (e.g. 12VDC) configured to provide power for starting vehicle 10 and to provideperipheral power to vehicle 10 during operation. The system battery 118provides power to actuator assembly 80 to move moveable sheave 102 tothe home position upon vehicle 10 being shutdown or being stopped andshifted into neutral. Primary clutch 50 of CVT 48 is also configured toreturn to a home position upon vehicle 10 suffering an abrupt powerloss, as described herein with reference to FIGS. 21-23.

In another embodiment, vehicle 10 does not have a system battery 118.For example, vehicle 10 may include a mechanical rope and recoilassembly that is pulled by an operator to start engine 42. Inparticular, the pull of the rope by an operator rotates a powergenerator that starts engine 42 of vehicle 10, and the power generator(driven by the rotating engine 42) provides peripheral power to theelectronic components of vehicle 10 during operation. See, for example,generator 304 of FIG. 22. As such, power from a system battery 118 isnot available to move primary clutch 50 to its home position whilevehicle 10 is shut down. In the illustrated embodiment, primary clutch50 is moved to its home position prior to shutting down vehicle 10 usingthe power provided with generator 304, as described herein.

Referring to FIG. 21, an exemplary control strategy 350 is illustratedfor moving primary clutch 50 to its home position in a vehicle 10 nothaving a system battery 118. Control strategy 350 is illustrativelyimplemented by controller 36 of FIG. 2, although another control unit ofvehicle 10 may be used. At block 352, an indicator (e.g. audible orvisual) is provided on vehicle 10 upon moving the vehicle key to the ONposition to indicate to the operator if primary clutch 50 is at its homeposition. In one embodiment, the indicator, such as a light, forexample, is powered by a small, low-voltage battery. The indicator mayalternatively be mechanically linked to the CVT 48 to detect theposition of clutch 50. If primary clutch 50 is at its home position,engine 42 is started by the operator, as illustrated at blocks 354, 356,and 358. For example, an operator may start engine 42 via a manual startsystem, such as a rope/recoil assembly or kick start assembly. In oneembodiment, actuation of the manual start system is blocked when primaryclutch 50 is not at its home position at block 352.

Upon an operator commanding engine 42 to stop at block 360 (e.g. turningthe vehicle key to OFF), primary clutch 50 automatically returns to itshome position at block 362 prior to controller 36 allowing engine 42 topower down. In particular, controller 36 executes a shut down sequenceat block 362 wherein controller 36 retains engine power despite theoperator commanding shutdown, moves sheave 102 of primary clutch 50 toits home position (i.e., with actuator assembly 80), and then allowsengine 42 to shut down (block 364). At block 366, engine 42 shuts down.Accordingly, primary clutch 50 is at the home position before engine 42shuts down such that vehicle 10 may be properly started up again at afuture time without having to reset clutch 50.

If primary clutch 50 is not at its home position at block 352, primaryclutch 50 must be moved to its home position prior to starting vehicle10, as illustrated at blocks 368, 370, and 372. For example, clutch 50may require a reset when vehicle 10 abruptly loses power beforecontroller 36 is able to reset clutch 50 to its home position. Primaryclutch 50 may be reset manually or automatically. In the manual reset ofblock 374, an operator removes cover 61 (see FIG. 5) of CVT 48 andmanually resets moveable sheave 102 to its home position by turningouter screw assembly 120 (see FIG. 5). In the automatic reset of block376, vehicle 10 includes an auxiliary power connection 330 (see FIG. 22)for connecting vehicle 10 to an external power supply (e.g. 12 VDC). Theexternal power supplied through auxiliary power connection 330 is routedto controller 36. Upon detecting the presence of external power,controller 36 moves primary clutch 50 to its home position via actuatorassembly 80. In one embodiment, power provided through auxiliary powerconnection 330 is routed directly to motor 76 of actuator assembly 80(see FIG. 2), and an operator manually controls actuator assembly 80with a switch or a diagnostic tool to move primary clutch 50 to the homeposition. At block 378, if primary clutch 50 is at the home position,the operator is able to start engine 42 at blocks 354 and 356. Ifprimary clutch 50 is not at the home position at block 378, the processreturns to block 372 for additional manual or automatic movement ofclutch 50.

Referring to FIG. 22, an exemplary control system 300 for a vehicle 10without a system battery 318 (FIG. 2) is illustrated. Control system 300illustratively includes a microcontroller 302 that controls a switch 320to selectively route power stored at a capacitor 316 to controller 36.Microcontroller 302 includes a processor and a memory accessible by theprocessor and containing software with instructions for monitoringvehicle power 306, detecting power interruption, and controlling switch320. Microcontroller 302 and controller 36 may alternatively beintegrated in a single controller. Generator 304, driven by engine 42(FIG. 2), provides vehicle power 306 (illustratively 12 VDC) forcontroller 36, microcontroller 306, and other peripheral components andfor charging capacitor 316. Capacitor 316 may alternatively be chargedby an external power supply via auxiliary connection 330. A fuse 308 anda diode 310, illustratively a Zener diode 310, are provided in seriesbetween vehicle 306 and controllers 302, 36 to provide reverse voltageprotection. A diode 312, illustratively a transient voltage suppressiondiode 312, is coupled between the output of diode 310 and ground toprovide over-voltage protection for controllers 302, 36. A resistor 314is provided for charging capacitor 316.

Microcontroller 302 is configured to close switch 320 upon detection ofa power loss at vehicle power 306. For example, upon vehicle 10 abruptlylosing power, microcontroller 302 senses the drop in vehicle power 306and closes switch 320. As a result, power stored at capacitor 316 isrouted to controller 36 for moving primary clutch of CVT 48 to the homeposition. In one embodiment, capacitor 316 is an ultra-capacitor.Capacitor 316 is alternatively a lithium ion battery or anotherlightweight battery that is smaller than a typical vehicle systembattery 318 (FIG. 2).

Referring to FIG. 23, an exemplary control strategy 400 is illustratedfor control system 300 of FIG. 22. With engine running at block 402, anoperator signals a vehicle shutdown at block 404, and the normalshutdown process for vehicle 10 is performed at block 406. For example,the shutdown process illustrated in blocks 360, 362, 364, and 366 ofFIG. 21 and described herein is performed at block 406 of FIG. 23. If anabrupt power loss is detected by controller 302 (FIG. 22) at block 410,controller 302 determines if capacitor 412 is charged and functioningproperly. If controller 302 determines capacitor 316 is not functioningproperly, switch 320 is not closed and primary clutch 50 is manuallymoved to its home position at block 418, as described with block 374 ofFIG. 21. If capacitor 316 is functioning properly at block 412,microcontroller 302 closes switch 320 to route power to controller 36 atblock 414. Controller 36 uses the power from capacitor 316 to driveactuator assembly 80 to move primary clutch 50 of CVT 48 to its homeposition. At block 416, controller 36 (or microcontroller 302)determines if clutch 50 is at its home position based on feedback from aposition sensor (e.g. sensor 290 of FIG. 20). If clutch 50 is at itshome position, the shutdown of vehicle 10 is determined to be proper atblock 408. If clutch 50 is not at its home position at block 416,process 400 proceeds to block 418 for a manual reset of clutch 50, asdescribed herein. In one embodiment, capacitor 316 is sized to containenough energy for moving clutch 50 to its home position based on a worstset of initial operating conditions where power interruptions couldoccur.

In one embodiment, vehicle 10 includes a mechanical return system forautomatically positioning primary clutch 50 at the home position uponsystem power being removed. For example, a mechanical spring/linkagesystem is coupled to moveable sheave 102 (see FIG. 5) of primary clutch50 to position primary clutch 50 in its home position upon vehicle 10being powered down. When power is returned to vehicle 10, controller 36operates normally to control primary clutch 50, as described herein.

While this invention has been described as having an exemplary design,the present invention may be further modified within the spirit andscope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains.

What is claimed is:
 1. A continuously variable transmission including: ashaft; and a clutch having a first sheave and a second sheave eachsupported by the shaft, the clutch further including a sliding assemblyand a screw assembly, the screw assembly and the sliding assembly beingconfigured to cooperate to move the second sheave relative to the firstsheave along the shaft, the sliding assembly including a bearingconfigured to move with the second sheave along the shaft, the screwassembly including a screw portion, the second sheave and the screwportion each having an outer profile, at least a portion of the bearingbeing positioned outside of the outer profile of the second sheave andat least a portion of the bearing being positioned inside the outerprofile of the screw portion.
 2. The transmission of claim 1, whereinthe bearing is an angular contact bearing.
 3. The transmission of claim1, wherein rotation of the screw assembly causes axial movement of thesecond sheave relative to the first sheave.
 4. The transmission of claim3, wherein the sliding assembly includes a bushing assembly coupled tothe shaft, and the bearing is positioned between the bushing assemblyand the screw portion of the screw assembly.
 5. A continuously variabletransmission including: a shaft; and a clutch having a first sheave anda second sheave each supported by the shaft, the second sheave having anouter profile and being configured to move relative to the first sheavealong the shaft, the clutch including a screw assembly having a screwportion, the screw assembly being configured to move the second sheaveaxially along the shaft, the clutch further including a bushing assemblyand a bearing configured to move with the second sheave, at least aportion of the screw portion of the screw assembly being axially betweenthe second sheave and the bearing.
 6. The transmission of claim 5,wherein the bearing is positioned between the screw portion of the screwassembly and the bushing assembly, and a rotation of the screw assemblycauses axial movement of the bushing assembly and the second sheaverelative to the first sheave.
 7. The transmission of claim 5, thebushing assembly including a neck portion configured to engage thebearing, the neck portion of the bushing assembly being positionedoutside of the outer profile of the second sheave.
 8. The transmissionof claim 7, the bushing assembly further including a shoulder portionadjacent the neck portion and a plurality of flanges extending from theshoulder portion and being coupled to the second sheave, the bearingbeing positioned adjacent the neck portion and the shoulder portion ofthe bushing assembly.
 9. The transmission of claim 5, wherein the clutchfurther includes a sliding assembly that cooperates with the screwassembly to move the second sheave along the shaft, the sliding assemblyincludes a plate portion, and the bushing assembly is coupled to theplate portion.
 10. The transmission of claim 9, further including asecond clutch and a belt coupled between the clutch and the secondclutch, wherein the sliding assembly of the clutch further includes atube portion positioned between the shaft and the second sheave, andwherein the belt moves between a first position adjacent the tubeportion and a second position away from the tube portion during movementof the second sheave along the shaft.
 11. The transmission of claim 1,wherein the bearing is positioned between the screw portion and theshaft.
 12. The transmission of claim 1, further including a secondclutch and a belt coupled between the clutch and the second clutch,wherein the second sheave of the clutch contacts the belt throughout theentire range of axial motion of the second sheave along the shaft. 13.The transmission of claim 1, further including a second clutch and abelt coupled between the clutch and the second clutch, the slidingassembly of the clutch including a tube portion positioned between theshaft and the second sheave, the belt moving between a first positionadjacent the tube portion and a second position away from the tubeportion during movement of the second sheave along the shaft.
 14. Acontinuously variable transmission including: a shaft; and a clutchhaving a first sheave and a second sheave each coupled to the shaft, thesecond sheave having an inner diameter near the shaft and an outerdiameter, the clutch further including a sliding assembly coupled to theshaft and to the second sheave, the sliding assembly and the secondsheave cooperating to form a sliding interface near the outer diameterof the second sheave, the sliding assembly being configured to transmita rotational force to the second sheave at the sliding interface torotate the second sheave.
 15. The transmission of claim 14, wherein thesecond sheave includes a plurality of ridges and the sliding interfaceincludes a plurality of clips configured to engage the plurality ofridges to form the sliding interface.
 16. The transmission of claim 14,wherein the sliding assembly and the second sheave cooperate to form aplurality of sliding interfaces circumferentially spaced near the outerdiameter of the second sheave, the rotational force being transmitted tothe second sheave at the plurality of sliding interfaces.
 17. Thetransmission of claim 14, wherein the sliding assembly includes a plateportion that cooperates with the second sheave to form the slidinginterface, and the plate portion is fixed axially relative to the shaftand the second sheave is moveable axially relative to the plate portionand to the shaft.
 18. The transmission of claim 17, wherein the plateportion transmits the rotational force from the shaft to the secondsheave at the sliding interface.
 19. The transmission of claim 14,wherein the second sheave includes a plurality of radially extendingprojections near the outer diameter, and the sliding assembly engagesthe plurality of radially extending projections to form a plurality ofsliding interfaces.
 20. The transmission of claim 14, wherein the clutchincludes a screw assembly configured to actuate axial movement of thesecond sheave along the sliding interface.
 21. The transmission of claim14, wherein the sliding interface includes a radially extending wall.22. A continuously variable transmission including: a first clutchincluding a first sheave and a second sheave moveable relative to thefirst sheave, the first clutch having an axis of rotation; a secondclutch; a belt coupled between the first and second clutches; and anactuator configured to move the second sheave of the first clutchrelative to the first sheave of the first clutch, the actuator beingpositioned between the first clutch and the second clutch and in a planeintersecting the first clutch and the second clutch, the plane beingnormal to the axis of rotation of the first clutch.
 23. The transmissionof claim 22, wherein the first clutch has an outer profile, and theactuator is positioned completely outside the outer profile of the firstclutch.
 24. The transmission of claim 22, wherein the actuator includesa motor, a reduction gear, and a gear shaft, the gear shaft beingpositioned between the first clutch and the second clutch and in theplane intersecting the first clutch and the second clutch.
 25. Thetransmission of claim 24, wherein the continuously variable transmissionfurther includes a housing, the first and second clutches are positionedin the housing, and at least a portion of the motor and at least aportion of the reduction gear are positioned outside of the housing. 26.The vehicle of claim 22, wherein the second clutch includes a firstsheave and a second sheave, the second sheave of the second clutch ismoveable relative to the first sheave of the second clutch, and theplane intersects the actuator, at least one of the first and secondsheaves of the first clutch, and at least one of the first and secondsheaves of the second clutch.
 27. The vehicle of claim 26, furtherincluding a housing, the first and second clutches being positioned inthe housing, the actuator including a motor and a gear shaft driven bythe motor, the gear shaft being positioned between the at least one ofthe first and second sheaves of the first clutch and the at least one ofthe first and second sheaves of the second clutch, and the motor beingpositioned outside the housing.
 28. The vehicle of claim 22, wherein thebelt forms a loop around the first and second clutches, and the actuatorextends through the loop formed by the belt.
 29. A recreational vehicleincluding: a chassis; a ground engaging mechanism configured to supportthe chassis; an engine supported by the chassis; a continuously variabletransmission driven by the engine, the continuously variabletransmission including a first clutch and a second clutch, the firstclutch being adjustable to modulate a gear ratio of the continuouslyvariable transmission; and an electro-hydraulic circuit configured tocontrol the first clutch, the electro-hydraulic circuit including amotor, a hydraulic pump driven by the motor, and an actuator driven bythe hydraulic pump and configured to adjust the first clutch, theactuator being coupled adjacent the continuously variable transmissionand at least one of the motor and the hydraulic pump being positionedaway from the continuously variable transmission.
 30. The vehicle ofclaim 29, wherein the actuator and the continuously variabletransmission are positioned at a first end of the vehicle, and the atleast one of the motor and the hydraulic pump is positioned at a secondend of the vehicle opposite the first end or at a middle portion of thevehicle between the first and second ends.
 31. The vehicle of claim 30,wherein the first end is the rear end of the vehicle and the second endis the front end of the vehicle, the first end includes an engine cover,and the engine, the continuously variable transmission, and the actuatorare positioned beneath the engine cover.
 32. The vehicle of claim 29,further including an cab portion supported by the chassis and havingside by side seating, wherein the at least one of the motor and thehydraulic pump are positioned beneath the side by side seating.
 33. Avehicle including: a chassis; a ground engaging mechanism configured tosupport the chassis; an engine supported by the chassis and having anoutput; a continuously variable transmission driven by the engine, thecontinuously variable transmission including a first clutch driven bythe engine, a second clutch driven by the first clutch, and a beltcoupled between the first and second clutches, the first clutch havingan interior region, the first clutch being adjustable to modulate a gearratio of the continuously variable transmission; and a centrifugalstarting clutch coupled to the output of the engine and positioned inthe interior region of the first clutch, the centrifugal starting clutchbeing configured to engage the first clutch upon a speed of the enginereaching a threshold speed.
 34. The vehicle of claim 33, wherein theengine includes an engine case and an output shaft extending outside theengine case, and the centrifugal starting clutch is coupled to theoutput shaft and is positioned entirely external to the engine case. 35.The vehicle of claim 33, wherein the continuously variable transmissionincludes a housing having a plurality of walls and an opening in atleast one of the plurality of walls, the first and second clutches andthe centrifugal starting clutch are positioned in the housing, and theoutput of the engine extends through the opening of the at least onewall and into the housing.
 36. The vehicle of claim 33, wherein thefirst clutch includes an inner wall forming the interior region, and thecentrifugal starting clutch contacts the inner wall of the first clutchto engage the first clutch upon the speed of the engine reaching thethreshold speed.
 37. The vehicle of claim 36, wherein the first clutchincludes a first sheave axially fixed and a second sheave axiallymoveable relative to the first sheave, and the first sheave includes theinner wall that forms the interior region for receiving the centrifugalstarting clutch.
 38. The vehicle of claim 33, wherein the first clutchfurther includes a first sheave, a second sheave, and a shaft supportingthe first and second sheaves, and the centrifugal starting clutch iscoupled to the shaft of the first clutch.
 39. The vehicle of claim 38,wherein the output of the engine includes an output shaft that isreceived by the shaft of the first clutch.